1. Field of the Invention
This invention relates to a torque adjuster adapted arbitrarily to adjust the magnitude of the torque of control means such as knobs or handles in a transmission device for transmitting the rotation of the handles through a rotary shaft to a rotatable member such as a pinion.
2. Description of the Prior Art
A torque adjuster adapted arbitrarily to adjust the magnitude of the torque of control means such as knobs or handles when a pinion is rotated by means of the control means is to be found, for example, in the operating handle portion of a microscope for vertically moving the object stage thereof. Description will therefore be made with reference to a microscope by way of example.
The torque of the control means or handles for vertically moving the object stage or the lens tube of a microscope has heretofore been adjusted to a predetermined value by the manufacturer. Thus, the user of the microscope could not readjust the torque of the operating handles to a magnitude (intensity) as he desires or a magnitude corresponding to observation. Also, on the part of the manufacturer, the adjustment of the torque of the operating control means to a predetermined value has been not only difficult, but it also required time, adjusting tools, etc.
FIG. 1 of the accompanying drawings shows a conventional driving device for the knobs for effecting longitudinal movement of the object stage of a microscope, for example, which has overcome the above-noted disadvantages. In this FIG., a stationary shaft 1 is integrally formed with an unshown microscope body. A pinion shaft 5 formed with a pinion 3 is rotatably fitted substantially centrally on the stationary shaft 1. This pinion 3 meshes with an unshown rack fixed to a vertically movable member such as an object stage or a lens tube. As shown, the pinion shaft 5 has tapered portions formed toward the opposite ends thereof, which ends are externally threaded at 7 and 9. Knobs 11 and 13 for effecting vertical movement are threadably fitted on the threads 7 and 9, respectively. The knobs 11 and 13 are also taper-coupled to the tapered portions of the pinion shaft 5.
Between the knobs 11, 13 and the stationary shaft 1, there are clearance in which friction members 15 and 17 are disposed. The friction forces resulting from the taper-coupling between the pinion shaft 5 and the knobs 11, 13 must be adjusted so as always to be greater than the friction forces between the knobs 11, 13 and the stationary shaft 1 resulting from the presence of the friction members 15 and 17. With the friction forces so adjusted, the pinion shaft 5 becomes rotatable upon rotation of the knobs 11, 13. The friction forces resulting from the taper-coupling prevent the knobs 11, 13 from being disengaged from the pinion shaft 5 even if the knobs are rotated in the direction in which they may be threadably disengaged. Adjustment of the torque output of the knobs 11, 13 may be accomplished by utilizing the resilient deformation between the pinion shaft 5 and the knobs 11, 13 in the taper-coupled portions. More specifically, the distance L.sub.1 may be reduced by rotating the knobs 11 and 13 in their mutually tightening direction, whereby the friction forces between the knobs 11, 13 and the stationary shaft 1 may be increased. Thus, the torque of the knobs 11, 13 may be increased.
However, the knobs 11 and 13 are rotated for each observation so that they rub against the friction members 15 and 17, and the wear thereof is increased with time and accordingly, the torque delivered by the knobs 11, 13 is decreased. For this reason, it is attempted to increase the knob torque by reducing the distance L.sub.1, but the taper-coupling between the knobs 11, 13 and the rotary shaft 5 permits the distance L.sub.1 to be reduced only slightly within the range allowed for by resilient deformation of these members, and not beyond such range. Thus, adjustment of the torque output of the knobs 11, 13 becomes impossible.